The present invention relates to a wine storage tank, particularly a wine storage tank which is particularly advantageous for use in processing red wine.
Red wine is obtained by crushing grapes and storing the crushed grapes in a tank in which the wine is left to ferment. The solution that results includes grape juice, seeds and skins. Leaving the skins in the solution imparts color and additional flavor to the wine and distinguishes the process from that used for making white wine.
During fermentation, the skins tend to float to the top of the tank, and after fermentation is complete clear wine is removed from the tank from a relatively small liquid discharge outlet at the bottom of the tank. Remaining in the tank is a mass of wet skins and seeds which amount to about 25% of the original volume of the solution. It is often desirable to let this sit for a period of time to extract as much juice runout as possible, so that the solid material may become relatively dry. However, this material must eventually be removed. This presents the problem that the solid material as it dries becomes increasingly difficult to remove from the tank.
This problem is typically solved by employing personnel to enter the tank, collect the material by raking or shoveling, and push the material through a specially adapted solids discharge outlet. An ancillary problem is that within the confined interior of the tank, these workers are exposed to a risk of asphyxiation from carbon dioxide created by the fermentation. It is often necessary, therefore, to remove this carbon dioxide before such entry is permitted.
Wine tanks typically have a flat floor that slopes about 1/2" per foot with respect to the horizontal. Very little slope is needed to drain liquids; however, solid material tends to stick to the walls of the tank and the gravity assist provided by such a slope is insufficient to permit the material to self-evacuate. Making the angle of the floor steeper facilitates sliding the material toward the bottom of the tank; however, a completely flat floor does not provide for directing the material to the outlet, so much of the material is stopped by the sidewall(s) of the tank, where it becomes stuck.
Like many types of tanks, wine tanks are typically formed of sheet metal. Sheet metal provides a good balance of cost and performance but complex forming in sheet metal can be expensive, especially for smaller runs. For example, shaping features into the floor to improve its capability for directing material to the outlet adds undesirably to the cost of manufacturing the tank.
Another problem with prior art wine tanks is that the flat floor must often be structurally enhanced underneath, because wine tanks can carry very heavy loads. Some wine tanks hold up to 25,000 gallons, or over 10 tons. On the other hand, frusto-conically shaped tanks which are stronger are also undesirably expensive to fabricate in sheet metal.
Accordingly, there is a need for a wine storage tank that provides for easier and less costly evacuation of solid material in the tank as well as decreased cost of manufacture.